REACTIVE POWER COMPENSATION

CONTENTS : 1) Introduction 2) Definition 3) What is reactive power 4) Real ,Reactive, Apparent Power 5) Power Triangle 6) Ways Of Reactive power Compensation 7) Benefits 8) Conclusion 9) References

INTROUDUCTION Major industrial loads ,for example, transformers, furnaces, induction motors etc need reactive power for sustaining magnetic field. Reactive power (VAR) compensation is defined as the management of reactive power to improve the performance of ac systems.

DEFINATION Reactive Power Compensation Device Any device which is connected in series or parallel with load and which is capable of supplying reactive power demanded by load is called reactive power compensation device.

WHAT IS REACTIVE POWER ? Power is referred as the product of voltage and current i.e. power = V x I The portion of power due to stored energy, which returns to the source in each cycle, is known as reactive power. In an ac transmission, when the voltage and current go up and down at the same time, only real power is transmitted and when there is a time shift between voltage and current both active and reactive power are transmitted. Reactive power, is due to the delay between voltage and current and cannot do useful work at the load. To distinguish reactive power from active power, it is measured in units of "volt-amperes reactive", (var). While reactive power does not provide useful work, it is a necessary component of power flow in an alternating current system. Reactive power required by customer load must be supplied in some way.

REAL, REACTIVE, AND APPARENT POWERS Reactive power is not delivered as effective mechanical power output unlike real power which is effectively converted as mechanical power output. The portion of power averaged over a complete AC waveform, is the real power; that is, energy that can be used to do work (for example overcome friction in a motor, or heat an element). On the other hand, the portion of power flow that is temporarily stored in the form of magnetic or electric fields, due to inductive and capacitive network elements, and then returned to source, is known as reactive power.

POWER TRIANGLE Power factor = cosø = real power / apparent power = kW/ kVA Whenever there is a phase shift between V and I we have:- a) real power (kW) b) reactive (imaginary ) power (kVAR) c) The combination is a complex or apparent power (kVA)=√(kW)² + (kVAR)²

THERE ARE TWO MAJOR WAYS OF REACTIVE POWER COMPENSATION Shunt compensation: Shunt capacitors are connected in parallel in the system and are used mainly for power factor improvement and in harmonic filters. It also boosts the voltage of the bus. This also known as load compensation. A shunt compensator is always connected in the middle of the transmission line.

Transmission line with shunt compensation

Series compensation Series capacitor are connected in series in the lines and are used mainly for boosting the receiving end voltage, increase in transmission capacity and reduction in losses in the lines. It also improve power factor at the sending end of the line. Unlike shunt capacitor whose output depends on the voltage, the voltage improvement by series capacitors increase with increase in load current. In other word the series capacitor is a self regulating type. Series compensation is also known as live compensation.

Transmission line with series compensation

FIXED COMPENSATION VS DYNAMIC COMPENSATION FIXED COMPENSATION:-Here the reactive power fed by the capacitors to the system is fixed. These are basically breaker controlled capacitors and are used in system which has constant load having a set pattern of operation. DYNAMIC COMPENSATION:-Here the reactive power fed by the capacitors to the system is dynamic. This is done using thyristor controlled capacitors. These are used in systems where the loads are fluctuating in nature like arc furnace loads.

BENEFITS OF REACTIVE POWER COMPENSATION Better efficiency of power generation, transmission and distribution Improvement in voltage Reduced KVA demand Higher load capability. Reduced system losses.

CONCLUSION From all the previous discussion we can conclude reactive power compensation is a must for improving the performance of the ac system. By reactive power compensation we can control the power factor and reduce the consumption of electricity.

References [1] Juan Dixon and Luis Moran -“ Reactive Power Compensation Technologies”. [2] Yongan Deng -“ Reactive Power Compensation Of Transmission Lines”. [3] Hong Chan- “ Practices of Reactive Power Management and Compensation”. T.J Millen- “ Reactive Power Control in Electrical Systems.” Canadian Electrical Association-Static Compensators For Reactive Power Control.

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